U.S. patent number 5,930,087 [Application Number 08/974,420] was granted by the patent office on 1999-07-27 for robust recording head for near-contact operation.
This patent grant is currently assigned to Hewlett-Packard Company. Invention is credited to Thomas C. Anthony, Manoj K. Bhattacharyya, James A. Brug, Lung T. Tran.
United States Patent |
5,930,087 |
Brug , et al. |
July 27, 1999 |
Robust recording head for near-contact operation
Abstract
A robust recording head with a spin tunneling sensing element
separated from an interface between the recording head and a
recording media so as not to be affected by collisions and other
ill effects at the interface between the recording head and the
recording media. The spin tunneling sensing element includes a pair
of magnetic elements wherein one of the magnetic elements functions
as a flux guide that conducts magnetic flux emanating from the
recording media away from the interface to an active area of the
spin tunneling sensing element.
Inventors: |
Brug; James A. (Menlo Park,
CA), Bhattacharyya; Manoj K. (Cupertino, CA), Tran; Lung
T. (Saratoga, CA), Anthony; Thomas C. (Sunnyvale,
CA) |
Assignee: |
Hewlett-Packard Company (Palo
Alto, CA)
|
Family
ID: |
25522020 |
Appl.
No.: |
08/974,420 |
Filed: |
November 20, 1997 |
Current U.S.
Class: |
360/324.2;
360/321; G9B/5.143; G9B/5.12; G9B/5.116; G9B/5.104; G9B/5.114;
G9B/5.106 |
Current CPC
Class: |
G11B
5/40 (20130101); B82Y 10/00 (20130101); G11B
5/3919 (20130101); B82Y 25/00 (20130101); G11B
5/33 (20130101); G11B 5/332 (20130101); H01F
10/3268 (20130101); G11B 5/3909 (20130101); G11B
5/3903 (20130101); G11B 5/3912 (20130101); G11B
5/11 (20130101); G11B 5/3967 (20130101); G11B
19/04 (20130101) |
Current International
Class: |
H01F
10/32 (20060101); G11B 5/40 (20060101); G11B
5/33 (20060101); H01F 10/00 (20060101); G11B
5/39 (20060101); G11B 5/10 (20060101); G11B
5/11 (20060101); G11B 19/04 (20060101); G11B
005/33 () |
Field of
Search: |
;360/113,126,127
;257/421 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolff; John H.
Claims
What is claimed is:
1. A recording head having a spin tunneling sensing element which
is integral with and spaced apart from an interface between the
recording head and a recording media, the spin tunneling sensing
element having a magnetic element that functions as a flux guide to
conduct magnetic flux emanating from the recording media away from
the interface to an active area of the spin tunneling sensing
element.
2. The recording head of claim 1, wherein the flux guide is coupled
to a pair of stabilization regions that set an orientation of
magnetization in the flux guide.
3. The recording head of claim 2, wherein an area of the flux guide
not coupled to the stabilization regions defines the active
area.
4. The recording head of claim 2, wherein the stabilization regions
comprise an antiferromagnetic material.
5. The recording head of claim 2, wherein the stabilization regions
comprise a pair of permanent magnets.
6. The recording head of claim 2, wherein the spin tunneling
sensing element further comprises a pinned magnetic film and an
intervening dielectric barrier.
7. The recording head of claim 6, wherein the pinned magnetic film
has an orientation of magnetization that is substantially
perpendicular to the orientation in the flux guide.
8. The recording head of claim 6, wherein the pinned magnetic film
includes a soft magnetic film coupled to layer of antiferromagnetic
material.
9. The recording head of claim 8, wherein the soft magnetic film
comprises a permalloy layer.
10. The recording head of claim 8, wherein the soft magnetic film
comprises a layer of nickel-iron.
11. The recording head of claim 8, wherein the antiferromagnetic
material is a manganese-base material.
12. The recording head of claim 8, wherein the antiferromagnetic
material is nickel-oxide.
13. The recording head of claim 8, wherein the antiferromagnetic
material is terbium-iron.
14. The recording head of claim 1, wherein the spin tunneling
sensing element is encased in a shield which is maintained at a
predetermined electrical potential and the flux guide is maintained
at the predetermined electrical potential to prevent short circuits
between the flux guide and the shield.
15. The recording head of claim 1, wherein the flux guide comprises
a soft magnetic film.
16. The recording head of claim 1, wherein the flux guide comprises
a permalloy layer.
17. The recording head of claim 1, wherein the flux guide comprises
a layer of nickel-iron.
18. The recording head of claim 1, further comprising a pair of
conductor layers that provide electrical connection to the spin
tunneling sensing element such that the conductor layers are
separated from the interface to prevent short circuits between the
recording media and the recording head.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention pertains to the field of recording heads.
More particularly, this invention relates to a robust recording
head suitable for near contact operations with recording media.
2. Art Background
Recording media such as magnetic tape and disk are commonly used in
a wide variety of information storage applications. Such a
recording media is usually constructed of a magnetically alterable
material that is capable of emanating a magnetic field or flux that
varies along its surface according to the content of the
information stored on the recording media. Such a recording media
is typically subdivided into storage areas or transitions.
Typically, the storage density of a recording media increases as
the surface dimensions of the storage areas on the recording media
decreases.
Information is usually read from such recording media with a
recording head that is positioned near the recording media as the
recording media moves with respect to the recording head. A
recording head typically includes a sensing element that senses the
magnetic flux emanating from the recording media. Typically, the
resistivity of the sensing element changes in response to the
magnetic flux emanating from the recording media. A sensing element
that changes resistivity in response to a magnetic field is usually
referred to as a magneto-resistive sensing element.
Prior magneto-resistive sensing elements typically include one or
more ferromagnetic elements whose resistivity changes in response
to magnetic flux. Prior magneto-resistive sensing elements include
anisotropic sensing elements in which a sense current flows along
planes of the ferromagnetic elements. Prior magneto-resistive
sensing elements also include spin tunneling sensing elements in
which a sense current flows perpendicular to the planes of the
ferromagnetic elements through a dielectric barrier.
The sensing element in prior recording heads, whether anisotropic
or spin tunneling, is usually positioned near the interface between
the recording head and the recording media where the intensity of
the magnetic flux being sensed is greatest. Typically, a recording
head and its sensing element must be positioned in near contact
with the recording media in order to sense weak magnetic fields and
in order to differentiate among different storage areas of a high
density recording media.
Collisions can occur between the recording head and the recording
media during such near contact operations, particulary with
removable recording media. Such collisions can result in
deformation of the sensing element which is typically located near
the interface to the recording media. Unfortunately, such
deformation can change the finely tuned magnetic properties of the
sensing element and reduce the sensitivity of the sensing element
to the magnetic flux emanating from the recording media. Such wear
to the sensing element can reach a point where the recording head
can no longer reliably read the recording media. Collisions between
the recording media and the sensing element can also introduce
thermal spikes into the sensing element. Unfortunately, such
thermal spikes usually cause a variation in the resistivity of the
sensing element, thereby introducing noise into the read
operation.
In addition, prior recording heads having a sensing element
positioned near the interface to the recording media are subject to
a variety of other ill effects. For example, such a sensing element
is often subject to damage from corrosion that occurs near the
interface to the recording media. Moreover, recording heads having
a sensing element near the recording media typically include
conductors which are placed near the interface to the recording
media. This can result in corrosion and smearing effects and can
result in short circuits between the conductors and the shields of
the recording head.
Furthermore, resistivity changes in a typical prior sensing element
usually gives rise to a voltage potential on the sensing element.
Such a potential on the sensing element may result in an electrical
short circuit between the sensing element and the shield of a prior
recording head. The potential difference between the sensing
element the shield can also cause a potential difference between
the sensing element and the recording media which can cause read
noise in the sensing element.
SUMMARY OF THE INVENTION
A robust recording head is disclosed that reduces problems
associated with collisions and other ill effects that occur at the
interface between the recording head an a recording media during
near contact operations. The recording head employs a spin
tunneling sensing element which is separated from the interface
between the recording head and the recording media so as not to be
affected by collisions and other ill effects at the interface
between the recording head and the recording media. The spin
tunneling sensing element includes a magnetic element that
functions as a flux guide to conduct magnetic flux emanating from
the recording media away from the interface to an active area of
the spin tunneling sensing element. The structure of the robust
recording head does not expose conductors for the sensing element
to the recording media and prevents short circuits from forming
between the flux guide and the recording head shields.
Other features and advantages of the present invention will be
apparent from the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is described with respect to particular
exemplary embodiments thereof and reference is accordingly made to
the drawings in which:
FIG. 1 shows a cross sectional view of a read portion of a
recording head that provides robust operation for near contact
applications to a recording media;
FIG. 2 shows a view of the flux guide and the pinned magnetic film
taken in a direction across the tracks of the recording media;
FIG. 3 is a detailed view of the layers encased in the shields of
the recording head including the layers of the spin tunneling
sensing element.
DETAILED DESCRIPTION
FIG. 1 shows a cross sectional view of a read portion of a
recording head 10 suitable for near contact operation with a
recording media 22. The recording head 10 is shown addressing a
surface 20 of the recording media 22. This cross section is taken
in a direction that traverses across a set of transitions 80-81 of
the recording media 22. The recording head 10 includes a flux guide
30 that conducts magnetic flux emanating from the surface 20 of the
recording media 22 upward and away from the surface 20. The flux
guide 30 in combination with a pinned magnetic film 32 and an
intervening dielectric barrier 34 form a spin tunneling
magneto-resistive sensing element (hereinafter tunnel sensor) in
the recording head 10. The tunnel sensor is encased in shields 12
and 14 of the recording head 10.
The area of the pinned magnetic film 32 that overlaps the flux
guide 30 defines an active region of the tunnel sensor. The
dielectric barrier 34 provides a thin tunnel barrier at the active
region of the tunnel sensor. The dielectric barrier 34 in on
embodiment is between 0.5 and 5 nanometers thick.
The pinned magnetic film 32 is pinned by an exchange layer (not
shown) of antiferromagnetic material. The exchange layer fixes the
orientation of magnetization of the pinned magnetic film 32. The
orientation of the magnetization in the pinned magnetic film 32 is
preferably orthogonal to the magnetization in the flux guide 30 in
the active region of the tunnel sensor in order to linearize the
sensing signal.
The flux guide 30 serves as one electrode of the tunnel sensor in
the recording head 10 and the pinned magnetic film 32 serves as the
other electrode. In one embodiment a pair of conductor layers 36
and 38 provide an electrical path for a sensing current that flows
through the tunnel sensor. The conductor layer 36 reduces leakage
of magnetic flux from the flux guide 30 to the shield 12 of the
recording head 10. Similarly, the conductor layer 38 serves to
reduce leakage of magnetic flux to the shield 14. In another
embodiment, the conductor layers 36 and 38 are not present and the
electrical sensing current flows directly via the flux guide 30 and
the magnetic film 32.
A sense current flows through the tunnel sensor while the recording
head 10 is reading the media 22. The sense current flows between
the pinned magnetic film 32 and the active region of the flux guide
30 across the dielectric barrier 34. Meanwhile, the flux guide 30
conducts magnetic flux emanating from the surface 20 up to the
active region of the tunnel sensor. This magnetic flux changes the
orientation of the magnetization in the active region of the flux
guide 30 and thereby changes the resistivity of the tunnel sensor
in the active region. The changing resistivity can be sensed by an
external sensing circuit (not shown) to provide a read signal from
the recording head 10.
The shields 12 and 14 are spaced apart by a dielectric region 16
which extends down to a surface 50 of the recording head 10. The
dielectric region 16 defines a gap width 40 in a direction along
tracks of the media 22 across the transitions 80-81. The surface 50
of the recording head 10 and the surface 20 of the media 22 define
a head/media interface.
The structure of the tunnel sensor in the recording head 10 makes
it possible to maintain the shields 12 and 14 and the flux guide 30
at the same electrical potential. This prevents the formation of
electrical short circuits between the flux guide 30 and the shields
12 and 14 at the head/media interface. In one embodiment, the
shields 12 and 14 and the flux guide 30 are all maintained at
ground potential while the conductor layer 36 is grounded and the
conductor layer 38 has a potential different from ground potential.
The greater the potential difference between ground and the
conductor layer 38 the better. Generally, this potential difference
is limited by the thickness of the dielectric region 16 and its
breakdown voltage.
The structure of the recording head 10 allows a very thin
dielectric region 16 and a very thin flux guide 30 which yields a
very thin gap width 40. The dielectric region 16 can be very thin
because it does not have to electrically isolate the flux guide 30
from the shields 12 and 14 due to their equal electrical
potentials. The flux guide 30 can also be made very thin because it
does not have to conduct sensing or bias currents along its plane.
These currents flow instead across the tunnel sensor. The
narrowness of the gap width 40 allows the recording head 10 to read
media with high densities. Therefore the length of the transitions
80-81 of the media 22 can be very small.
The structure of the recording head 10 also prevents collisions and
other ill effects at the head/media interface from affecting the
efficiency of the tunnel sensor. The active region of the tunnel
sensor in the recording head 10 is far enough away from the
head/media interface so as not to be susceptible to collisions
between the media 22 and the recording head 10. Collisions that may
damage portions of the flux guide 30 near the head/media interface
do not affect the active region and therefore do not substantially
affect the response of the tunnel sensor to magnetic flux emanating
from the surface 20 of the media 22. In addition, the thermal
effects caused by collisions between the recording head 10 and the
media 22 are far enough removed from the active region of the
tunnel sensor to prevent thermal spikes from introducing
substantial noise into the sensing current that flows through the
tunnel sensor.
In addition, the active region of the tunnel sensor in the
recording head 10 is isolated from corrosion that may occur at the
head/media interface. Moreover, the recording head 10 does not
expose the conductor layers 36 and 38 to the head/media interface.
This avoids the effects caused by conductor smearing or short
circuits that commonly occur in prior recording heads.
FIG. 2 shows a view of the flux guide 30 and the pinned magnetic
film 32. This cross section is taken in a direction across the
tracks of the media 22 along one of the transitions 80-81. Regions
42 and 44 represent the stabilization regions of the flux guide 30.
The read width for the tunnel sensor is defined by the regions of
the flux guide 30 that are not pinned by the stabilization regions
42 and 44. The read width corresponds to the width of tracks on the
media 22 in a dimension orthogonal to that of the transitions
80-81.
In one embodiment, the stabilization regions 42 and 44 are realized
by layers of antiferromagnetic material. The antiferromagnetic
material may be a manganese-based material such as iron-manganese
(FeMn), nickel-manganese (NiMn), or iridium-manganese,
Alternatively, the antiferromagnetic material may be nickel-oxide
or terbium-iron (TbFe).
In another embodiment, the stabilization regions 42 and 44 are
realized by permanent magnets.
An arrow labeled M1 shows the direction of magnetization in the
active region of the flux guide 30. The direction shown for M1 is
along the longest dimension of the flux guide 30 which is across
the tracks of the media 22. The direction shown of M1 is set by the
stabilization regions 42 and 44 and varies about the direction
shown in response to magnetic flux emanating from the media 22.
An arrow labeled M2 shows the direction of magnetization in the
pinned magnetic film 32. The orientation of magnetization M2 is
pinned by an antiferromagnetic layer and is substantially
orthogonal to M1 in the active region of the flux guide 30.
FIG. 3 is a detailed view in one embodiment of the layers encased
in the shields 12 and 14 of the recording head 10. This view
depicts the active region of the tunnel sensor. The base of the
structure is a dielectric layer that provides a portion of the
dielectric region 16. Next is the conductor layer 36 which is made
of a conductive material such as gold. A thin layer of tantalum 64
prevents diffusion between the conductor layer 36 and the flux
guide 30.
The flux guide 30 is a layer of soft magnetic film. In one
embodiment, the flux guide 30 is a permalloy layer such as
nickel-iron. A pair of thin iron layers 66 and 68, which in one
embodiment are each 20 .ANG. thick, are used at the interfaces
between the dielectric barrier 34 and the layers 30 and 32.
The dielectric barrier 34 is a layer of dielectric material. In one
embodiment, the dielectric barrier is a layer of aluminum-oxide
(Al.sub.2 O.sub.3).
The pinned magnetic film 32 is a layer of soft magnetic film. In
one embodiment, the pinned magnetic film 32 is a permalloy layer
such as nickel-iron.
The orientation of the magnetization in the pinned magnetic film 32
is pinned by an antiferromagnetic layer 60. In one embodiment, the
antiferromagnetic layer 60 is a layer of manganese-based material
such as iron-manganese (FeMn), nickel-manganese (NiMn), or
iridium-manganese, Alternatively, the antiferromagnetic layer 60
may be a layer of nickel-oxide or terbium-iron (TbFe).
On top of the antiferromagnetic layer 60 is the conductor layer 38
which may be tantalum or tantalum/gold.
The direction of magnetization M1 in the flux guide 30 at the
head/media interface allows magnetic flux to be conducted directly
into the flux guide 30 and eliminates the need for biasing
structures and methods for reducing cross-track asymmetry. In
addition, the total power consumption of the recording head 10 is
relatively low because a tunnel sensor is a relatively high
impedance structure. A low power consumption recording head may be
useful for tape heads in which many parallel channels may
exist.
The foregoing detailed description of the present invention is
provided for the purposes of illustration and is not intended to be
exhaustive or to limit the invention to the precise embodiment
disclosed. Accordingly, the scope of the present invention is
defined by the appended claims.
* * * * *